1. Field of the Invention
The present invention relates to an ink-jet recording head configured to generate droplets of a recording liquid applicable to ink-jet recording and relates to a method for producing the head.
2. Description of the Related Art
In general, ink-jet recording heads applicable to ink-jet recording each include a minute recording-liquid-discharging nozzle (hereinafter, referred to as a “discharge port”), a liquid passage, and a liquid-discharge-energy-generating portion disposed at part of the liquid passage. Hitherto, a method described in U.S. Pat. No. 4,657,631 has been known as a method for producing such an ink-jet recording head.
The method described in U.S. Pat. No. 4,657,631 includes forming a liquid passage pattern with a soluble resin, coating the pattern with an epoxy resin or the like and effecting curing, cutting a substrate, and removing the soluble resin by dissolution. According to the method, bonding and cutting are performed while the ink passage is filled with the soluble resin. Thus, problems such as intrusion of adhesives or dust into the ink passage and chipping or cracking of the ink discharge port are prevented.
A method including forming an ink passage pattern with a positive resist, coating the passage pattern with a photocurable resin, forming a nozzle (ink nozzle) on an energy-generating element by photopatterning, and eluting the positive resist to form an ink passage has been reported as an advanced method. In this method, the ink passage and the nozzle (ink nozzle) are formed not by cutting but by photolithography; hence, processing can be performed with very high accuracy.
As described in U.S. Pat. No. 6,390,606, in some cases, to increase adhesion to a coating resin layer covering an ink passage pattern, an adhesion-improving-layer pattern composed of a thermoplastic resin is formed on a substrate including an energy-generating element.
In the case where an ink passage is formed by forming an ink passage pattern composed of a positive resist and then removing the ink passage pattern by dissolution, it goes without saying that the ink passage pattern should have shape stability as a mold in order to form the ink passage with high accuracy. However, during patterning of the coating resin layer, the resin layer partially transmits light to inevitably expose the positive resist constituting the ink passage pattern to light. This may cause reducing a chemical change of part of the positive resist, the shape stability as a mold, and thus degrading the shape accuracy of the ink passage.
In the case where the adhesion-improving-layer pattern is formed, in some cases, the molecular weight of part of the ink passage pattern is reduced by light reflected from the adhesion-improving-layer pattern. Furthermore, a crack may form during the development of the coating resin layer. In some cases, the crack causes an abnormality of the discharge port shape, thus resulting in nonuniformity of the discharge direction of the ink droplets discharged and reducing the size of the ink droplets discharged. This may result in a nonuniform image.
In recent years, trends toward improvements in the quality of images obtained by ink-jet recording have required a reduction in the volume of the ink droplets to be discharged and an increase in droplet landing accuracy. Thus, the ink passages have been required to have higher shape accuracy. Therefore, ink passage patterns have been required to have higher shape stability as molds.